Refractometer



FIG. 1 is a rear perspective view of a refractometer showing my new design;

FIG. 2 is a front left top perspective view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a rear elevational view thereof;

FIG. 6 is a left side elevational view thereof, the right side being identical. 

The ornamental design for a refractometer, as shown and described. 